It is known in the art that melt-processable polymers which exhibit an anisotropic (i.e., an ordered) melt phase can be melt-extruded through an extrusion die to form fibers, films, and three-dimensional shaped articles which substantially exhibit the same cross-sectional shape as that of the extrusion orifice. Such products of melt-extrusion commonly exhibit higher tensile modulus values than similar articles prepared from more common polymers which exhibit no anisotropy in the melt phase. Also, it has been found that polymers that exhibit no anisotropy in the melt phase usually cannot satisfactorily be melt-extruded to form elongated solid three-dimensional shaped articles which possess the desired cross-sectional configuration.
Representative prior disclosures which concern the formation of melt-extruded fibers from a polymer that is capable of forming an anisotropic melt phase are commonly assigned U.S. Pat. Nos. 4,083,829; 4,161,470; 4,219,461; 4,256,624; 4,330,457; and 4,473,682. A representative disclosure which concerns the formation of melt-extruded films from a polymer capable of forming an anisotropic melt phase is commonly assigned U.S. Pat. No. 4,332,759. Representative prior disclosures that concern the formation of melt-extruded three-dimensional shaped articles from a polymer which is capable of forming an anisotropic melt phase are commonly assigned U.S. Ser. No. 364,824, filed Apr. 2, 1982, and U.S. Pat. No. 4,468,364.
It has heretofore been observed in the prior art that, when large elongated articles (e.g., elongated rods) are melt-extruded from a polymer which is capable of forming an anisotropic melt phase, the resulting articles exhibit substantially lesser modulus values expressed in psi than do fibers that are melt-extruded from the same polymer. For instance, a melt-extruded filament of the anisotropic melt-forming wholly aromatic polyester of U.S. Pat. No. 4,161,470 of approximately 15 denier (i.e., a diameter of approximately 0.0015 inch) following heat treatment commonly will exhibit a tensile modulus of approximately 9,000,000 to 9,900,000 psi. A melt-extruded rod of the same polymer of U.S. Pat. No. 4,161,470 having a diameter of approximately 0.06 inch following heat treatment commonly will exhibit a tensile modulus of only approximately 3,500,000 to 4,000,000 psi. Also, a melt-extruded filament of the anisotropic melt-forming wholly aromatic poly(ester-amide) of U.S. Pat. No. 4,330,457 of approximately 4.2 denier (i.e., a diameter of approximately 0.0008 inch) following heat treatment commonly will exhibit a tensile modulus of approximately 10,500,000 to 11,700,000 psi. A melt-extruded rod of the same polymer of U.S. Pat. No. 4,330,457 having a diameter of approximately 0.06 inch following heat treatment commonly will exhibit a tensile modulus of only approximately 6,000,000 to 7,000,000 psi. Such disparities in tensile modulus values are also apparent prior to heat treatment.
It is an object of the present invention to provide an improved process for the melt-extrusion of large solid elongated shaped articles from a polymer which exhibits an anisotropic melt phase.
It is an object of the present invention to provide an improved process for the melt-extrusion of large solid elongated shaped articles from a polymer which exhibits an anisotropic melt phase wherein non-isothermal conditions within the polymer prior to solidification are substantially minimized.
It is an object of the present invention to provide an improved process for the melt-extrusion of large solid elongated shaped articles from a polymer which exhibits an anisotropic melt phase wherein the resulting product exhibits an enhanced tensile modulus.
It is an object of the present invention to provide an improved process for the melt-extrusion of large solid elongated shaped articles from a polymer which exhibits an anisotropic melt phase wherein the resulting product exhibits an enhanced tensile modulus in the substantial absence of melt-fracture during the formation thereof.
It is another object of the present invention to provide an improved process for the melt-extrusion of large solid elongated shaped articles from a polymer which exhibits an anisotropic melt phase wherein more uniform polymeric orientation is accomplished throughout the cross-section of the resulting product.
It is a further object of the present invention to provide an improved extrusion die for the melt-extrusion of improved large elongated articles comprising a polymer which is capable of forming an anisotropic melt phase.
These and other objects, as well as the scope, nature, and utilization of the claimed invention will be apparent to those skilled in the art from the following detailed description and appended claims: